Substrate having fluid dam adapted for use an electro wetting display device

ABSTRACT

An electrowetting display device includes a first substrate comprising a wall pattern surrounding a pixel electrode disposed in a display area of the first substrate, a spaced apart second substrate comprising a common electrode and a dam member disposed in a peripheral area surrounding the display area. The dam member has sealable openings (a.k.a. sealable dam spillways) through which there is discharged an excess portion of an excessively supplied wetting layer, the discharge of the excess occurring while the first and second substrates are brought together about top and bottom portions of a sealing ring that seals them together.

This application is a divisional application of U.S. patent applicationSer. No. 13/656,190 filed on Oct. 19, 2012, which claims priority toKorean Patent Application No. 10-2012-0066741, filed on Jun. 21, 2012,in the Korean Intellectual Property Office (KIPO), and all the benefitsaccruing therefrom under 35 U.S.C. §119, the contents of the priorapplications being herein incorporated by reference

BACKGROUND

1. Field of Disclosure

The present disclosure of invention relates to a substrate for anelectrowetting display device. More particularly, the present disclosurerelates to an electrowetting display device having improved reliability.

2. Description of Related Technology

An electrowetting display device displays a desired image by selectivelydisplacing parts of plural fluid layers where the parts include a polar(e.g., hydrophillic) fluid and a nonpolar (e.g., hydrophobic) fluid.Generally, the electrowetting display device includes a first substrateon which a plurality of pixel electrodes are formed, a spaced apartsecond substrate on which a common electrode is formed, a hydrophillic(polar, and thus electrostatically movable) upper fluid layer isinterposed between the first and second substrates, and discrete amountsof a nonpolar (e.g., hydrophobic) fluid are disposed at each of thepixel electrodes where at least one of the fluids is dyed. When anappropriate voltage is applied between a respective pixel electrode andthe common electrode, a normal surface tension state of the polar (e.g.,hydrophillic) upper fluid is overcome and it is displaced so that theadjacent nonpolar (e.g., hydrophobic) fluid is also moved to make wayfor the electrostatically displaced upper fluid and this causes thecorresponding pixel to transmit or block a supplied light. Thus, theelectrowetting display device may display an image.

Processes of manufacturing the electrowetting display device includesfully filling the fluid layers (where “fluid” here means liquid) into afilling space defined by a containerizing structure disposed on thefirst substrate and combining the first substrate and second substrateunder pressure. During this pressurized combination process, anundesired bursting of a sealant which combines the first substrate withthe second substrate may occur if there an excess of internal pressurein the filling space during the process of bonding together (combining)the substrates. In addition, if the sealant does not burst, a middleportion of the electrowetting display device may be undesirably bulgedby a non-contact remnant of the combining pressure so that a cell gap ofthe electrowetting display device may be non-uniform across its displayarea.

It is to be understood that this background of the technology section isintended to provide useful background for understanding the heredisclosed technology and as such, the technology background section mayinclude ideas, concepts or recognitions that were not part of what wasknown or appreciated by those skilled in the pertinent art prior tocorresponding invention dates of subject matter disclosed herein.

SUMMARY

The present disclosure of invention provides an electrowetting displaydevice capable of keeping uniform a cell gap across its display areaeven if an excess of wetting fluid is applied during assembly of theelectrowetting display device.

According to an exemplary embodiment, there is provided a firstsubstrate comprising a wall pattern surrounding a pixel electrode anddisposed in a display area of the device, a spaced apart secondsubstrate comprising a common electrode, a sealing ring joining thefirst substrate to the second substrate and sealing in a whetting fluidinterposed between the first and second substrate; and a dam memberdisposed in a peripheral area surrounding the display area and havingsealable openings through which an excess amount of the whetting fluidcan be discharged, where the whetting fluid includes a nonpolar firstfluid layer and a polar second fluid layer.

In an exemplary embodiment, the dam member has a polygon shape withsides of the polygon being disposed in areas corresponding to four edgesof the display area.

In an exemplary embodiment, wherein the dam openings each have a widthof about 0.03 mm to about 1 mm.

In an exemplary embodiment, the electrowetting display device mayfurther include a gap maintaining member maintaining a predetermined gapbetween the first substrate and the spaced apart second substrate.

In an exemplary embodiment, the gap maintaining member is disposed inthe display area and aligned with the wall pattern.

In an exemplary embodiment, a height of the dam member is substantiallythe same as a height of the gap maintaining member.

In an exemplary embodiment, the first fluid layer includes a hydrophobicfluid and the second fluid layer comprises a hydrophillic fluid.

In an exemplary embodiment, the first fluid layer is disposed in a firstfilling space which is formed by the wall pattern and the second fluidlayer is normally disposed in a second filling space formed by the gapmaintaining member.

According to still another exemplary embodiment, there is provided afirst substrate comprising a wall maintaining pattern surrounding apixel electrode disposed in a display area and a dam member disposed ina peripheral area surrounding the display area. The wall maintainingpattern provides a predetermined spacing apart between the first andsecond substrates as well surrounding each pixel-electrode. The dammember and the wall maintaining pattern are formed from a same materialand protrude from a same one of the first and second substrates.

In an exemplary embodiment, the electrowetting display device furtherincludes a sealing protecting pattern including a first protecting damdisposed at a first side of the sealing area and a second protecting damdisposed at an opposed second side of the sealing area.

In an exemplary embodiment, a height of the dam member is substantiallythe same as a height of the wall maintaining member.

In an exemplary embodiment, the first fluid layer includes a nonpolar(e.g., hydrophobic liquid) and the second fluid layer includes a polar(e.g., hydrophillic) liquid.

According to one aspect of the present disclosure of invention, duringassembly of the electrowetting display device, an excessive amount ofthe wetting fluid is provided between the first and second substratesbefore they are squeezed together and against top and bottom sides ofthe sealant ring. The dam member has openings (spillways) through whichan excess part of the wetting fluid is discharged as the first andsecond substrates are joined to each other by way of the sealant ringand at the same time the sealant closes up the openings. As a result ofthis assembly process, a bursting of the sealant due to excess pressuremay be prevented and a cell gap of the wetting layer may be kept uniformover the whole of the display area. In addition, an adhesion surfacearea size between the dam member and the sealant may be increased by theopening parts so that an adhesive strength between the first and secondsubstrates may be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present disclosure ofinvention will become more apparent by describing in detailed exemplaryembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a plan view illustrating an exemplary embodiment of anelectrowetting display device according to the present disclosure ofinvention;

FIG. 2 is a cross-sectional view illustrating the electrowetting displaydevice taken along line I-I′ in FIG. 1;

FIG. 3 is a plan view illustrating a second substrate in FIG. 2;

FIG. 4A, FIG. 4B and FIG. 4C are cross-sectional views explaining onemanufacturing method of the second substrate shown in FIG. 2;

FIG. 5A and FIG. 5B are cross-sectional views explaining onemanufacturing method of the electrowetting display device in FIG. 1;

FIG. 6 is a cross-sectional view illustrating an electrowetting displaydevice according to another exemplary embodiment;

FIG. 7 is a plan view illustrating a first substrate in FIG. 6;

FIG. 8A and FIG. 8B are cross-sectional views explaining onemanufacturing method of the first substrate shown in FIG. 6;

FIG. 9 is a cross-sectional view illustrating an electrowetting displaydevice according to another exemplary embodiment; and

FIG. 10 is a plan view illustrating a first substrate in FIG. 9.

DETAILED DESCRIPTION

Hereinafter, the present disclosure of invention will be provided ingreater detail with reference to the accompanying drawings.

FIG. 1 is a plan view illustrating an exemplary embodiment of anelectrowetting display device according to the present disclosure. FIG.2 is a cross-sectional view illustrating the electrowetting displaydevice taken along line I-I′ in FIG. 1.

Referring to FIGS. 1 and 2, the electrowetting display device includes afirst substrate 110, a second substrate 120 and a wetting layer 130. Thewetting layer 130 is disposed between the first and second substrates110 and 120. The electrowetting display device includes a display areaDA configured for displaying an image and a peripheral area PAsurrounding the display area DA. The display area DA includes aplurality of pixel areas configured for displaying the image by anelectrowetting displacement method and the peripheral area PA includes asealing area SA in which a sealant is disposed for sealing in thewetting layer 130.

The first substrate 110 includes a first base substrate 111, a gate lineGL, a data line DL, a switching element SW, a pixel electrode PE, anotch electrode NE, a wall pattern 116 and a sealant SL (which in oneembodiment, may be composed of stacked portions SL1 and SL2 as shall beexplained). The first substrate 110 further includes a first passivationlayer 112 and a second passivation layer 114.

The gate line GL, the data line DL, the switching element SW, the pixelelectrode PE, notch electrode NE and the wall pattern 116 are disposedin the display area DA of the first base substrate 111. The sealant SLis disposed in the sealing area SA of the first base substrate 111.

The gate line GL (one of a parallel many, only one shown) is extended ina first direction D1 and the data line DL (one of a parallel many, onlyone shown) is extended in a second direction D2 crossing the firstdirection D1. The switching element SW of each pixel is electricallyconnected to the pixel's corresponding gate line GL and to the pixel'scorresponding data line DL.

The first passivation layer 112 is disposed on the first base substrate111 on which the switching element SW is formed. The pixel electrode PEis disposed on the first passivation layer 112.

The pixel electrode PE is disposed in the pixel area P of the first basesubstrate 111 and is electrically connected to the switching element SWthrough a contact hole formed in the first passivation layer 112. Thus,a data voltage transferred through the data line DL may be applied tothe pixel electrode PE when the corresponding gate line is activated forcausing such transfer.

The notch electrode NE is disposed on the first passivation layer 112and is disposed adjacent to the pixel electrode PE. The notch electrodeNE may receive a substantially same voltage as a voltage applied to thecommon electrode 124 of the second substrate 120.

The second passivation layer 114 is disposed on the first base substrate111 on which the pixel electrode PE and the notch electrode NE areformed. The second passivation layer 114 may have a hydrophobic uppersurface so that, in a normal state, a correspondingly hydrophobic one(or otherwise nonpolar one, 131) of the two fluids (131, 132) is causedto spread out over (wet) the floor area of the hydrophobic upper surfaceof the second passivation layer 114 in its respective pixel cell area.

The wall pattern 116 is disposed on the second passivation layer 114.The wall pattern 116 (which can be rectangular or another closed shapewhen viewed from a top plan view) is disposed along (around) an edge ofthe pixel area P and forms a first filling space FS1.

The sealant SL (which in one embodiment, may be composed of stackedportions SL1 and SL2 as shall be explained) is disposed in the sealingarea SA included in the peripheral area PA. The sealant SL, when fullycured, combines (bonds together) the first substrate 110 with the secondsubstrate 120. However, during assembly, the sealant SL may be at leastpartially uncured and thus still soft and pliable such that relativelyrigid protrusions DD of a dam member can be press inserted into theuncured sealant material.

The second substrate 120 includes a second base substrate 121, a lightblocking pattern BM (black matrix), a color filter CF, a commonelectrode CE, a gap maintaining member CS and a dam member DD.

The blocking pattern BM is disposed on the second base substrate 121 anddivides the second base substrate 121 into a matrix of lighttransmission areas and light blocking areas. An area in which theblocking pattern BM is disposed may be defined the blocking area and theblocking pattern BM overlaps with the wall pattern WP. The transmissionarea defined by the blocking pattern BM may correspond to the apertureof the pixel area. In addition, the blocking pattern BM may be disposedin the peripheral area PA of the second base substrate 121.

The color filter CF may be disposed in the pixel area P defined by theblocking pattern 122.

The common electrode CE is disposed on the second base substrate onwhich the color filter CF is formed. The common electrode CE is oppositeto the pixel electrode PE and the notch electrode NE.

The gap maintaining member (spacer) CS overlaps with the blockingpattern BM and is disposed on the common electrode CE. The gapmaintaining member CS overlaps with the wall pattern 116. The gapmaintaining member CS uniformly maintains a gap between the firstsubstrate 110 and the second substrate 120 and forms a second fillingspace FS2.

The dam member DD (which has relatively rigid protrusion also denoted asDD) is disposed in the peripheral area PA of the second base substrate121 and, in one embodiment, rests on top of a lower portion SL1 of thesealant layers (SL1+SL2). The dam member DD includes a plurality ofopening parts OP between its protrusion parts such as openings having anarrow slit shape. The size of the openings OP may depend on a viscosityof the second fluid layer 132 when the latter is being excessivelyfilled into the devices during assembly and thereafter partly expelledby way of still-not-blocked parts of the openings OP (a.k.a. damspillways). Basically, during assembly, the dam member DD functions asan intentionally leaky (but not too leaky) boundary member and the dammember DD is disposed as such an intentionally leaky boundary member inthe peripheral area PA of the second base substrate 121 corresponding tothe sealing area SA. The sealant SL disposed in the sealing area SA andan upper portion SL2 of the sealant SL may be progressively filled moreand more into the opening parts OP of the dam member DD after the secondfluid layer 132 is injected into the device during assembly and asexcess portions of the second fluid layer 132 are expelled by way ofstill-unblocked portions of the dam spillways (openings OP).

More specifically, during the assembly process, the opening parts OP ofthe dam member DD operate as tiny passageways through which an excessportion of the wetting layer 130 is discharged to an outside as thefirst and second substrates are being joined to each other underpressure. The wetting layer 130 is initially filled in to a thickerheight dimension than the predetermined gap between the first and secondsubstrates 100 and 200 and the excess fluid spills out through the damspillways defined by the opening parts OP as the first and secondsubstrates are pressed together. Therefore, due to this last minuteexpulsion of excess fluid, the electrowetting display device may beprevented from being damaged by an excessive increasing of an internalpressure of the wetting layer 130 due to excess fluid being present whenthe first and second substrates are joined to each other under pressure.Examples of the damages caused by the excessive increasing of theinternal pressure may include bursting of the sealant SL (in the casewhere there are no dam spillways OP), excessive bulging of a middleportion in the display area of the electrowetting display device due toexcess fluid being retained there and so on.

As mentioned, the wetting layer 130 includes a first fluid layer 131such as a dyed (e.g., black) hydrophobic liquid (e.g., a dark coloredoil) and a second fluid layer 132 such as a clear (e.g., transparent)hydrophillic liquid.

The first fluid layer 131 is disposed in a lower layer region betweenthe first and second substrates 110 and 120 and is filled in the firstfilling space FS1 formed by the wall pattern 116 (where the outersurfaces of wall pattern 116 and the upper surface of second passivationlayer 114 are nonpolar (e.g., hydrophobic)). For example, thehydrophobic first fluid layer 131 may be a black-dyed nonpolar organicliquid (e.g., an oil). The polar (e.g., hydrophillic) second fluid layer132 is normally disposed in an upper layer region between the first andsecond substrates 110 and 120 and is filled in the second filling spaceFS2 formed by the gap maintaining member CS. This is the normal state ofthe polar (e.g., hydrophillic) second fluid layer 132 because it isrepelled by the nonpolar (e.g., hydrophobic) surface portion of the wallpattern 116 and of the second passivation layer 114 s well as by thenonpolar (e.g., hydrophobic) first fluid layer 131.

The state shown in FIG. 2 is the normal state wherein there is nopotential difference between the common electrode 124 and the pixelelectrode PE. Then, under this electric field free condition, thenonpolar first fluid layer 131 is relaxed and wets the nonpolar (e.g.,hydrophobic) walls in the first filling space FS1 and thus generallyspreads out uniformly in the pixel area P in which the pixel electrodePE and the notch electrode NE are formed. Thus, a light transmitted fromthe second substrate 120 is blocked by the darkly-dyed first fluid layer131 so that the pixel area P may display an image having a black grayscale. However, when a potential difference (voltage) of adequatemagnitude is formed between the common electrode 124 and the pixelelectrode PE, the field-attracted second and polar fluid layer 132 ispulled into the first filling space FS1 to thereby displace thehydrophobic first fluid layer 131 from that area so that the latter one(131) gathers toward the wall pattern 116 adjacent to the notchelectrode NE in the pixel area. A size of the gathered the first fluidlayer 131 is changed according to the potential difference voltage sothat a transmittance of the light transmitted from the second substrate120 may be changed. Thus, the pixel area P may display images havingvarious gray scales.

FIG. 3 is a plan view illustrating just the second substrate 120 of FIG.2.

Referring to FIGS. 2 and 3, the dam member DD is disposed in theperipheral area PA of the second substrate 120. For example, the dammember DD may be disposed in the sealing area SA.

The dam member DD is disposed to define a slightly leaky enclosure alongthe four side edges of the display area DA such as a quadrangular shape.The dam member DD includes between its relatively rigid protrusions, aplurality opening parts OP such as those having the narrow slit shape.For example, each of opening parts has a width of about 0.03 mm to about1 mm. The dam member DD may have the substantially same height dimensionas a height of the gap maintaining member CS. The gap maintaining memberCS (e.g., protruding spacer poles) and the protrusions of the dam memberDD may respectively each have a respective height dimension of about 15μm. As will be better understood in conjunction with the embodimentstate shown in FIG. 5B, the height dimension of the dam member DD comesto rest on top of the height dimension of a lower layer portion SL1 ofthe sealant and subsequently, after excess amounts of the second fluid132 are released through the spillways (OP), the upper layer portion SL1of the sealant is added and/or cured.

The opening parts OP of the dam member DD operate as the passageways(spillways) through which the excess amounts of the wetting layer 130are discharged to the outside during the pressure driven joiningtogether (combining) of the first and second substrates 110, 120.Therefore, the electrowetting display device may be prevented from beingdamaged by an excess increasing in an internal pressure of the wettinglayer 130. Examples of the damages caused by the increasing the internalpressure may include burst of the sealant SL, bulging of a middleportion in the display area of the electrowetting display device and soon. According to the present exemplary embodiment, the electrowettingdisplay device after the combination process being finished may have thewetting layer 130 of a uniform thickness and the right amount of fluidvolume for it as needed by the predetermined filling spaces (FS1 plusFS2) of the device.

The dam member DD may be formed in the sealing area SA via a processsubstantially the same as, and using substantially same materials asthat of forming the gap maintaining member CS disposed in the displayarea DA.

FIG. 4A, FIG. 4B and FIG. 4C are cross-sectional views explaining onemanufacturing method of the second substrate shown in FIG. 2. (It is tobe understood that that the display area DA is generally much wider andhas many more pixel areas across it and that the illustrated cross overfrom the display area DA to the surrounding peripheral area PA isschematic in nature and in particular the discontinuity illustrated inFIG. 4B for the common electrode layer CE is schematic in nature whereasin actuality a smoother transition of vertical position is providedfor.)

Referring to FIGS. 2 and 4A, a light blocking material layer is blanketformed on a base substrate 121. The blocking layer is patterned into thematrix-like blocking pattern BM. The blocking pattern BM aligns with thewall pattern 116 in the display area DA and may be generally formed inthe peripheral area PA.

Referring to FIGS. 2 and 4B (where these are schematic in nature), acolored photoresist layer is formed on the base substrate 121 on whichthe blocking pattern BM is formed. The colored photoresist layer ispatterned into the correspondingly colored filter CF and the colorfilter CF is formed in an area corresponding to the pixel area P of thebase substrate 121. After plural runs, the color filter CF may includered, green and blue filters.

The common electrode CE is blanket formed on the base substrate 121 onwhich the color filter CF is formed. The common electrode CE may includea transparent conductive material such as ITO or IZO. The commonelectrode CE may be formed in only the display area DA or in all thedisplay area DA and the peripheral area PA. Not shown in figures, anover coating layer may be formed on the base substrate 121 on which thecolor filter CF is formed so as to flatten (planarize) the secondsubstrate 120.

Referring to FIGS. 2 and 4C, an organic layer is formed to apredetermined thickness on the base substrate 121 on which the commonelectrode CE is formed, the predetermined thickness being at least asthick as the planned height dimensions of the spacers CS and of thespaced apart dam portions (spaced apart by OP). The organic layer ispatterned into the gap maintaining members CS in the display area DA andthe dam member portions DD in the peripheral area PA.

The gap maintaining members CS overlaps with and align with the wallpattern 116 of the first substrate 110.

The dam member DD is formed in the peripheral area PA of the basesubstrate 121 corresponding to the sealing area SA of the firstsubstrate 110. The dam member DD may be formed along at least one offour edges of the display area DA. For example, the dam member DD may beformed along all four edges of the display area DA. In an alternateembodiment, the entire periphery of the dam does not have to be leaky(due to openings OP) and instead such openings are provided in only aportion of the formed dam.

The dam member DD may have the substantially same height as a height ofthe gap maintaining member CS. For example, the dam member DD may havethe height of about 15 μm.

The dam member DD includes the opening parts OP such as the slit shapes.The width of the opening parts OP may be set based on a combination ofdesired discharge speed, viscosity and the excess thickness of thewetting layer excessively formed in the combination process. Forexample, the width of the opening part OP may be about 0.03 mm to about1.0 mm.

FIG. 5A and FIG. 5B are cross-sectional views explaining onemanufacturing method of the electrowetting display device in FIG. 1.

Referring to FIG. 5A, the first substrate 110 includes a pixel area Pdisposed in the display area DA. In the pixel area P, a switchingelement SW, a pixel electrode PE, a notch electrode NE and a wallpattern 116 are disposed.

A partial sealant SL1 or a still not fully cured and thus tacky, fullheight SL is formed in the peripheral area PA of the first substrate110. The sealant SL (or SL1) is disposed in the sealing area SA of thefirst substrate 110.

The second substrate 120 includes the gap maintaining member CS formedin the display area DA and the dam member DD formed in the peripheralarea PA.

After the partial sealant SL1 or a still not fully cured and thus tacky,full height sealant SL is formed on the first substrate 110, the firstfluid layer 131 is formed (deposited) in the first filling spaces(cavities) FS 1 formed by the wall pattern 116. The second fluid layer132 is thereafter formed (deposited) on the first substrate 110 on whichthe first fluid layer 131 is formed. The second fluid layer 132 is fullformed to an excess amount on the first substrate 110.

A process method by which the first and second fluid layers 131 and 132are formed on the first substrate 110 may be various depending onviscosities, surface tension effects and so on.

For example, after the first substrate 110 is put in a bath, a firstfluid such as the oil is put in the bath. Then, a second fluid such asan electric field movable electrolyte is filled in the bath. Thus, thefirst fluid layer 131 is filled in the first filling space FS1 formed bythe wall pattern 116 and the second fluid layer 132 is fully formed toan excess amount on the first substrate 110 to cover the first fluidlayer 131.

Alternatively, using a coating method, the first and second fluid layers131 and 132 may be formed. According to the coating method, a firstfluid such as the oil is dropped (e.g., ink jet wise) in the firstfilling space FS1 formed by the wall pattern 116 on the first substrate110 so that the first fluid layer 131 is formed in the pixel area P.Using a slit coating, a second fluid such as a hydrolyte is formed to athick thickness on the first substrate 110 on which the first fluidlayer 131 is formed.

Alternatively, using a dual slit method, the first and second fluidlayers 131 and 132 may be formed on the first substrate 110 at the sametime. For example, a first inkjet head drops the first fluid layer 131in the first filling space FS1. A second inkjet head moves following thefirst inkjet head and drops the second fluid layer 132 to a thickthickness on the first substrate 110 on which the first fluid layer 131is formed.

As described above, the first and second fluid layers 131 and 132 may beformed on the first substrate 110 by various methods.

Referring to FIG. 5B, using the combination process, the secondsubstrate 120 formed the gap maintaining member CS and the dam member DDis combined with the first substrate 110. In this case, the sealant SLmay be formed in various ways including pre-hardening a lower layerportion SL1 as pre-bonded to the first substrate 110 and then adding anot-yet fully hardened upper layer portion SL2 into which the more rigiddam member protrusions are going to be pushed at the same time thatexcess fluid 130 is discharged through what remains as unblocked (stillopen but diminishing in size of non-blockage) dam openings OP.

In one embodiment, when the second substrate 120 is combined with thefirst substrate 110, the dam member DD is combined with (pushed into)the still uncured top portion of the sealant SL and the gap maintainingmember CS is combined with (makes contact with) the wall pattern 116.When the first and second substrates 110 and 120 are combined with eachother, the second fluid layer 132 fully formed is discharged to theoutside through what is left of the diminishing in size unblockedportions of the opening parts OP of the dam member DD. Therefore, theelectrowetting display device may be prevented from being damaged byincreasing an internal pressure of the wetting layer 130, such as burstof the sealant SL, bulging of a middle portion in the display area ofthe electrowetting display device and so on.

When a combination of the first and second substrates 110 and 120 isfinished, the remainder of the sealant SL (e.g., at least the stilltacky upper part) is filled into the disappearing opening areas OP ofthe dam member DD to fully adhere to and seal up the dam member DD sothat an adhesion of the first and second substrates 110 and 120 isfinished. By the sealant SL being filled to cover the protrusion surfaceareas between the opening parts OP, an adhesion size between the firstand second substrates 110 and 120 may be increased so that an adhesivestrength between the first and second substrates 110 and 120 may beincreased. The curing of the sealant SL is then driven to completion ifso desired at this stage of manufacture.

FIG. 6 is a cross-sectional view illustrating an electrowetting displaydevice according to another exemplary embodiment in accordance with thepresent disclosure of invention. FIG. 7 is a plan view illustrating afirst substrate in FIG. 6.

Hereinafter, the same reference numerals are used to refer to the sameor like parts as those described in the previous exemplary embodiments,and the same detailed explanations are omitted or simplified.

Referring to FIGS. 6 and 7, the electrowetting display device includes afirst substrate 110, a second substrate 120 and a wetting layer 130.

The first substrate 110 includes a first base substrate 111, a gate lineGL, a data line DL, a switching element SW, a pixel electrode PE, anotch electrode NE, a wall maintaining pattern 117 and a dam member DD.The first substrate 110 further includes a first passivation layer 112and a second passivation layer 114.

The wall maintaining (spacers plus cavity formation) pattern 117according to the present exemplary embodiment, replace and thus performsubstantially same functions as those of the wall pattern 116 and of thegap maintaining pattern CS according to the previously exemplaryembodiment shown in FIG. 2 except that here the dam protrusions DD andthe wall maintaining pattern 117 arise from the first substrate 111rather than descending from the second substrate 120.

The wall maintaining pattern 117 is disposed along edges of the pixelarea P to form a filling space (first fluid containing cavity)corresponding to the pixel area. The wetting layer 130 is filled in thefilling space. The wetting layer 130 is the substantially same as thatof the previously exemplary embodiment. The wetting layer 130 mayinclude a first fluid layer 131 such as a dark colored and non-polar oiland a second fluid layer 132 such as a polar electrolyte covering thefirst fluid layer 131.

A height of the wall maintaining pattern 117 is substantially the sameas the sum of the heights of the wall pattern 116 and the gapmaintaining pattern CS according to the previously exemplary embodimentshown in FIG. 2. For example, the height of the wall maintaining pattern117 may be about 19 μm to about 20 μm.

The dam member DD according to the present exemplary embodiment isdisposed in the peripheral area PA of and attached to the first basesubstrate 111. For example, the dam member DD is disposed in the sealingarea SA included in the peripheral area PA of the second substrate.

The dam member DD may be disposed along at least one of four edges ofthe display area DA. For example, the dam member DD may be disposedalong all four edges of the display area DA.

The dam member DD includes a plurality of opening parts OP such as aslit shape, and has the height being substantially same as the height ofthe wall maintaining pattern 117. For example, the dam member DD mayhave the height of about 19 μm to about 20 μm.

The opening part OP of the dam member DD may be filled by the sealant SLdisposed in the sealing area SA. In the combination process, the openingparts OP of the dam member DD become passages through which the wettinglayer 130 formed thicker than the predetermined gap between the firstand second substrates 100 and 200 is discharged to an outside as thefirst and second substrates are brought together during assembly.Therefore, the electrowetting display device may be prevented from beingdamaged by increasing an internal pressure of the wetting layer 130,such as burst of the sealant SL, bulging of a middle portion in thedisplay area of the electrowetting display device and so on. The widthof the opening part OP may be set so as to smoothly discharge the excessportion of the wetting layer 130 based on a combination speed and thethickness of the wetting layer excessively formed in the combinationprocess. For example, the width of the opening part OP may be about 0.03mm to about 1 mm.

According to the present exemplary embodiment, the second substrate 120includes a second base substrate 121, a blocking pattern BM, a colorfilter CF and a common electrode CE. The sealant SL according to thepresent exemplary embodiment is disposed so as to be aligned with thesealing area SA included in the peripheral area PA of the second basesubstrate 121.

FIG. 8A and FIG. 8B are cross-sectional views explaining onemanufacturing method of the first substrate shown in FIG. 6.

Referring to FIGS. 7 and 8A, the switching element SW is formed on thebase substrate 111 and the switching element SW is connected to the gateline GL and the data line DL. The first passivation layer 112 is formedon the base substrate 111 on which the switching element SW is formedand a contact hole is formed in the first passivation layer 112. Thepixel electrode PE and the notch electrode are formed on the firstpassivation layer 112. The pixel electrode PE is electrically connectedto the switching element SW through the contact hole.

Referring to FIGS. 7 and 8B, the second passivation layer 114 (e.g.,having a surface that is wettable by a nonpolar liquid 131) is formed onthe base substrate 111 on which the pixel electrode PE and the notchelectrode NE are formed.

An organic layer is formed on the base substrate 111 on which the secondpassivation layer 114 is formed. The organic layer is patterned into thewall maintaining pattern 117 in the display area DA and the dam memberDD in the peripheral area PA. The organic layer may be transparent oropaque.

The wall maintaining pattern 117 is disposed along edge of the pixelarea P defined on the base substrate 111 to form the filling space.

The dam member DD may be disposed along at least one of four edges ofthe display area DA. For example, the dam member DD may be disposedalong all four edges of the display area DA. The dam member DD includesa plurality of opening parts OP between its relatively rigid protrusionsand the width of the opening parts OP may be set so as to smoothlydischarge the excess wetting layer 130 based on a combination speed andthe thickness of the wetting layer excessively formed in the combinationprocess. For example, the width of the opening part OP may be about 0.03mm to about 1 mm.

The height of the wall maintaining pattern 117 is the substantially sameas the height of the dam member DD. For example, the wall maintainingpattern 117 and the dam member DD may have the height of about 19 μm toabout 20 μm.

According to the present exemplary embodiment, the wall maintainingpattern 117 and the dam member DD are formed using the relatively thickorganic layer first deposited as a single layer structure and thereafterpatterned. However, not shown in the figures, the wall pattern of afirst thickness may be formed in the he display area DA using a firstorganic layer of the first thickness. Then, the gap maintaining patternof a second thickness may be formed on the wall pattern of the firstthickness using a second organic layer of the second thickness and thedam member DD of the second thickness may be formed in the peripheralarea PA using the second organic layer of the second thickness. Thus,the wall maintaining pattern 117 in the display area DA may have adouble layer structure comprising the wall pattern of the firstthickness and the gap maintaining pattern of the second thickness. Thedam member DD of the second thickness in the peripheral area PA may havethe single layer structure.

According to the present exemplary embodiment, when the dam member DD iscombined with the sealant SL (which is at least partially uncured inareas where the dam protrusions are driven into the sealant) and the gapmaintaining member CS is combined with the wall pattern 116 in thecombination process, the excess part of the wetting fluid 130 which wasintentionally excessively filled into the upper filling space FS2, isdischarged to the outside through the opening parts OP of the dam memberDD as the first and second substrates are brought into union with oneanother. Therefore, the electrowetting display device may be preventedfrom being damaged by increasing an internal pressure of the wettinglayer 130. Examples of the damages caused by the increasing the internalpressure may include burst of the sealant SL, bulging of a middleportion in the display area of the electrowetting display device and soon. In addition, an adhesion size between the dam member DD and thesealant SL may be increased due to increased surface area created by theopening parts OP so that an adhesive strength between the first andsecond substrates 110 and 120 may be increased.

FIG. 9 is a cross-sectional view illustrating an electrowetting displaydevice according to yet another exemplary embodiment. FIG. 10 is a planview illustrating a first substrate in FIG. 9.

Hereinafter, the same reference numerals are used to refer to the sameor like parts as those described in the previous exemplary embodiments,and the same detailed explanations are omitted or simplified.

The electrowetting display device according to the present exemplaryembodiment further includes a sealing protecting pattern in compare withthe electrowetting display device according to the previously exemplaryembodiment shown in FIG. 6.

The electrowetting display device according to the present exemplaryembodiment includes a first substrate 110, a second substrate 120 and awetting layer 130.

The first substrate 110 is the substantially same as that of thepreviously exemplary embodiment shown in FIGS. 6 and 7.

The second substrate 120 according to the present exemplary embodimentincludes a second base substrate 121, a blocking pattern BM, a colorfilter CF, a common electrode CE and a sealing protecting pattern SPPwhose cross sectional shape may be seen in FIG. 9.

The sealing protecting pattern SPP is disposed in the peripheral area PAof the second base substrate 121. For example, the sealing protectingpattern SPP includes a first protecting (non-leaky) dam PD1 and a secondprotecting (non-leaky) dam PD2. The first protecting dam PD1 is disposedbetween the display area and the sealing area SA and is disposed along afirst side portion of the sealing area SA. The second protecting dam PD2is disposed adjacent to a second side portion of the sealing area SA andis disposed along the second side portion of the sealing area SA. Thesealing protecting pattern SPP may be disposed along at least one offour edges of the sealing area SA. For example, the sealing protectingpattern SPP may be disposed along all four edges of the sealing area SA.A height of the sealing protecting pattern SPP may be equal to or lessthan the predetermined gap between the first and second substrates 110and 120.

The sealing protecting pattern SPP may be used to prevent a bursting ofthe still-uncured, at least upper part of the sealant SL as the leakydam protrusions DD are pushed into that portion of the sealant SL. Thecross sectional shapes shown in FIG. 9 are exemplary and of course othershapes including tapered ones may be used.

According to the exemplary embodiments of the present disclosure ofinvention, in the process of bringing the first and second substratesinto union with one another, an excess portion of the wetting layer isdischarged to the outside through the opening parts of the dam member sothat a sealant burst may be prevented and a cell gap of the wettinglayer may be kept of uniform dimension across the whole of the displayarea (DA). In addition, an adhesion surface size between the dam memberand the sealant may be increased by the opening part so that an adhesivestrength between the first and second substrates may be increased.

The foregoing is illustrative of the present disclosure of invention andis not to be construed as limiting thereof. Although a few exemplaryembodiments of the present teachings have been described, those skilledin the art will readily appreciate from the foregoing that manymodifications are possible in the exemplary embodiments withoutmaterially departing from the novel teachings and advantages of thepresent disclosure. Accordingly, all such modifications are intended tobe included within the scope of the present teachings. In the claims,means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents but also functionally equivalent structures.

What is claimed is:
 1. An electrowetting display device comprising: afirst substrate including a wall maintaining pattern forming aliquid-retaining cavity surrounding a pixel electrode disposed in adisplay area of the first substrate, the wall maintaining pattern alsodefining spacers that keep the first substrate spaced apart from anoverlying structure by a predetermined gap distance; a dam memberdisposed in a peripheral area of at least one of the first and secondsubstrates, the peripheral area surrounding the display area, where thedam member defines one or more sealable openings extending therethrough;a second substrate including a common electrode disposed for creating anelectric field with the pixel-electrode of the first substrate, thesecond substrate being part of the overlying structure that is spacedapart from the first substrate; a sealant disposed in the peripheralarea and filling the sealable openings of the dam member; and a wettingfluid layer disposed between the first and second substrates, thewetting fluid layer comprising a nonpolar first fluid layer and a polarsecond fluid layer.
 2. The electrowetting display device of claim 1,wherein the dam member is disposed in areas corresponding to four edgesof the display area.
 3. The electrowetting display device of claim 1,wherein the openings each have a width of about 0.03 mm to about 1 mm.4. The electrowetting display device of claim 1, wherein the sealant isdisposed in the peripheral area and provides adheres to each of thefirst and second substrates.
 5. The electrowetting display device ofclaim 4, wherein the dam member is disposed in a sealing area in whichthe sealant is disposed.
 6. The electrowetting display device of claim5, wherein the second substrate further comprises: a sealant protectingpattern including a first protecting dam disposed at a first side of thesealing area and a second protecting dam disposed at an opposed secondside of the sealing area.
 7. The electrowetting display device of claim1, wherein the wall maintaining pattern maintains a predetermined gapbetween the first substrate and the second substrate.
 8. Theelectrowetting display device of claim 7, wherein a height of the dammember is the substantially same as a height of the wall maintainingmember.
 9. The electrowetting display device of claim 8, wherein thefirst fluid layer comprises a hydrophobic fluid and the second fluidlayer comprises a hydrophillic fluid.
 10. The electrowetting displaydevice of claim 9, wherein the first fluid layer is disposed in afilling space being formed by the wall maintaining pattern and thesecond fluid layer is normally disposed on top of the first fluid layer.